Jigsaws generally include a housing containing a motor for driving a saw blade in a reciprocating manner. A shoe, having a generally flat lower surface for location against a workpiece to be cut by the saw, is mounted to the housing of the saw, and forms a reaction surface such that when the saw blade moves away from the workpiece, the shoe forms a reaction surface to enable cutting action, whereas when the blade moves towards the workpiece, debris produced by the cutting action is displaced from the vicinity of the blade.
In order to enable bevel cutting of a workpiece, it is desirable to provide a shoe which is pivotable relative to the housing about a longitudinal axis, and a clamping mechanism for clamping the shoe in one or more desired orientations relative to the saw blade. In this way, when the shoe rests on a workpiece, bevel cutting at an angle corresponding to the angle of inclination between the shoe and the saw housing is also possible.
DE 19546162 discloses a clamping mechanism for a shoe of a jigsaw in which a shoe can be clamped in a plurality of orientations relative to a housing of the jigsaw by means of rotation of a double threaded screw about its longitudinal axis by means of a lever. Rotation of the lever in one direction causes the shoe to be clamped in position between a clamping plate and the housing, whereas rotation of the lever in the opposite direction increases the separation between the clamping plate and the housing to allow the shoe to be pivoted relative to the saw blade.
However, this prior art arrangement suffers from the drawback that the provision of a screw having oppositely wound threads increases the cost of production of the apparatus, and the provision of a lever pivoting about the longitudinal axis of the double threaded screw still limits the extent to which the lever can be rotated in the space available between the shoe and the saw housing.
EP 0603552 discloses a shoe clamping mechanism for a saw in which rotation of a screw thread about a first axis to clamp a shoe in position relative to a saw housing is achieved by rotation of a rotatable hand grip about a second axis perpendicular to the first axis. Cooperating conical gears parallel to each axis ensure that rotation of the hand grip about the second axis causes rotation of the screw thread about the first axis. This arrangement suffers from the drawback, however, that conical gears are expensive components to manufacture and must be located relatively accurately relative to each other, since the focuses of the two conical gears must generally coincide with each other to ensure correct operation. As a result, this significantly increases the cost of production of a saw incorporating the clamping mechanism.
EP 0970771 discloses a jigsaw base clamping system in which a shoe is fixed in a predetermined orientation relative to a saw housing by means of a clamping mechanism incorporating moveable wedge shaped ramps. This arrangement suffers from the drawback that the large number of cooperating moving parts significantly increases the cost of production of a tool incorporating the mechanism.
Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.